[PATCH v3 6/6] Documentation: dmaengine: document DMA_CTRL_ACK
From: robert.jarzmik@free.fr (Robert Jarzmik)
Date: 2015-05-14 17:55:03
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lkml
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
Add documentation about acking the transfers, and their reusability. Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr> --- Documentation/dmaengine/provider.txt | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/Documentation/dmaengine/provider.txt b/Documentation/dmaengine/provider.txt
index 05d2280..33a81ce 100644
--- a/Documentation/dmaengine/provider.txt
+++ b/Documentation/dmaengine/provider.txt@@ -345,11 +345,12 @@ where to put them) that abstracts it away. * DMA_CTRL_ACK - - Undocumented feature - - No one really has an idea of what it's about, besides being - related to reusing the DMA transaction descriptors or having - additional transactions added to it in the async-tx API - - Useless in the case of the slave API + - if set, the TX transfer can be reused after being completed. + - there is a guarantee the TX won't be freed until it is acked + by async_tx_ack() + - as a consequence, if a device driver wants to skip the dma_map_sg() and + dma_unmap_sg() because the DMA'd data wasn't used, it can resubmit the + transfer right after its completion. General Design Notes --------------------
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2.1.4